Method for manufacturing liquid crystal display device

ABSTRACT

The present invention provides a method for manufacturing a liquid crystal display device capable of suppressing display unevenness around a seal in the case of performing PS treatment on a horizontal alignment film formed from a photoactive material. The method for manufacturing a liquid crystal display device of the present invention includes the steps of: forming a horizontal alignment film containing a photoactive material on at least one substrate of a pair of substrates; dropping a liquid crystal composition containing a liquid crystal material and a monomer on one of the pair of substrates, the monomer being contained in an amount of 1.0% by weight or less in the whole liquid crystal composition; curing a sealing material applied to one substrate of the pair of substrates along an outer edge thereof by irradiating the sealing material with light whose wavelength is 40 nm or more longer than an absorption wavelength edge of the monomer; and forming a polymer layer that controls the alignment of liquid crystal molecules adjacent thereto on the horizontal alignment film by irradiating the liquid crystal composition sealed between the pair of substrates with light to polymerize the monomer.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a liquidcrystal display device. More specifically, the present invention relatesto a method for manufacturing a liquid crystal display device suitablefor the cases of forming a polymer layer for improving properties on ahorizontal alignment film that is formed by photo-alignment treatment.

BACKGROUND ART

Liquid crystal display (LCD) devices are display devices which controlthe alignment of birefringent liquid crystal molecules to control thetransmission/shielding of light (on/off of display). Examples of displaymodes of the LCDs include a vertical alignment (VA) mode in which liquidcrystal molecules with negative anisotropy of dielectric constant arealigned vertically to a substrate surface; an in-plane switching (IPS)mode and a fringe field switching (FFS) mode, in which liquid crystalmolecules with positive or negative anisotropy of dielectric constantare aligned horizontally to a substrate surface and a horizontalelectric field is applied to a liquid crystal layer.

Among these modes, a multi-domain vertical alignment (MVA) modeutilizing liquid crystal molecules with negative anisotropy ofdielectric constant and alignment-regulating structures (e.g. banks(ribs), hollow portions (slits) of electrodes) is capable of aligningthe liquid crystal molecules in multiple directions during voltageapplication even without rubbing treatment on an alignment film, and isexcellent in viewing angle characteristic. In conventional MVA-LCDs,however, upper portions of the ribs or upper portions of the slits serveas the boundaries of alignment division of the liquid crystal molecules,deteriorating the transmissivity during white-image display and causingdark lines in displayed images. Thus, there is room for improvement.

Therefore, alignment-stabilizing techniques using a polymer(hereinafter, also referred to as polymer sustained (PS) techniques)have been suggested as methods of producing LCDs with high luminance andhigh response speed (for example, see Patent Literatures 1 to 8). In apre-tilt-angle-imparting technique using a polymer (hereinafter, alsoreferred to as a polymer sustained alignment (PSA) technique) amongthese PS techniques, a liquid crystal composition containing apolymerizable component such as a polymerizable monomer and oligomer issealed between the substrates, and the monomer is polymerized with theliquid crystal molecules being tilted (inclined) by a voltage appliedbetween the substrates, thereby forming a polymer. This provides liquidcrystal molecules tilted with a predetermined pre-tilt angle even afterthe voltage application is stopped, and the alignment direction of theliquid crystal molecules is controlled to a certain direction. Themonomer is selected from a material polymerizable by heat, light(ultraviolet light). The liquid crystal composition may contain apolymerization initiator for initiating the polymerization of themonomer (for example, see Patent Literature 4).

On the other hand, a photo-alignment technique has been recently studiedas a technique for achieving an excellent viewing angle characteristic;this technique is capable of aligning the liquid crystal molecules inmultiple directions during voltage application even without rubbingtreatment on an alignment film, and is capable of achieving an excellentviewing angle characteristic. The photo-alignment technique is atechnique in which an alignment film is formed from a photoactivematerial and the film is irradiated with light (e.g. ultraviolet light),thereby giving an alignment-regulating force to the alignment film.

Some recent papers disclose that combination use of such aphoto-alignment (PA) technique, a rubbing technique, and theaforementioned PS technique for improving the alignment stability inliquid crystal display devices of the IPS mode can provide good results(for example, see Non-Patent Literature 1).

CITATION LIST Patent Literature

-   Patent Literature 1: Japanese Patent No. 4175826-   Patent Literature 2: Japanese Patent No. 4237977-   Patent Literature 3: JP 2005-181582 A-   Patent Literature 4: JP 2004-286984 A-   Patent Literature 5: JP 2009-102639 A-   Patent Literature 6: JP 2009-132718 A-   Patent Literature 7: JP 2010-33093 A-   Patent Literature 8: U.S. Pat. No. 6,177,972

Non-Patent Literature

-   Non-Patent Literature 1: Y. Nagatake, et al, ITE and SID,    “Hysteresis Reduction in EO Characteristics of Photo-Aligned    IPS-LCDs with Polymer-Surface-Stabilized Method”, IDW '10, 89-92,    LCT p 2-5, 2010. 12

SUMMARY OF INVENTION Technical Problem

The current photo-alignment technique has been adopted mainly for massproduction of TVs using a vertical alignment film (e.g. VA mode) and hasnot yet been adopted for mass production of TVs using a horizontalalignment film (e.g. IPS mode). This is because the use of a horizontalalignment film causes large-scale image sticking in liquid crystaldisplay. The image sticking is the following phenomenon: when a constantvoltage is continuously applied to a part of a liquid crystal cell for acertain period of time and then the whole image is changed to anotherimage, the brightness at the portion where the voltage has beencontinuously applied seems to differ from the brightness at the portionwhere no voltage has been applied.

FIG. 6 is a schematic view showing the state of image sticking in aliquid crystal cell of an IPS mode produced with photo-alignmenttreatment. As shown in FIG. 6, the brightness at the portion withvoltage (AC) application significantly differs from that at the portionwithout voltage (AC) application, and it is found that image stickingoccurs to an extremely large degree in the portion with voltage (AC)application. Suppression of image sticking requires formation of apolymer layer that has a stable alignment-regulating force obtained bythe PS technique, and this requires promotion of the polymerization forPS step.

The present inventors thus have studied introduction of a polymerstabilization (PS) step in production of a liquid crystal cell of theIPS mode obtained by photo-alignment treatment; in this step, apolymerizable monomer is added to a liquid crystal, and thepolymerizable monomer is polymerized by heat or light to form a polymerlayer on the surface constituting the boundary with the liquid crystallayer. FIG. 7 is a schematic view showing the state of image sticking ina liquid crystal cell of an IPS mode produced with photo-alignmenttreatment and a PS step. As shown in FIG. 7, the brightness is hardlydifferent between the portion with voltage (AC) application and theportion without voltage (AC) application, and it is found that imagesticking at the portion with voltage (AC) application is greatlysuppressed. As mentioned here, introduction of the PS step into aconventional method greatly suppresses image sticking.

The present inventors have performed various studies on causes oflarge-scale image sticking especially in liquid crystal cells of the IPSmode, and thereby have found that image sticking in liquid crystal cellsof the IPS mode and that in liquid crystal cells of the VA mode arecaused by different mechanisms. In the VA mode, image sticking occursdue to remaining (memory) of the tilt in the polar angle direction; inthe IPS mode, image sticking occurs due to remaining (memory) of thealignment in the azimuth direction and formation of an electrical doublelayer. The present inventors have further studied to have found thatthese phenomena are attributed to the material of a photo-alignmentfilm.

The present inventors have furthermore studied to have found that theimprovement effects of the PS step are especially effective with analignment film formed from a photoactive material; for example, theimprovement effects of the PS step are not achieved with an alignmentfilm which is formed from a photoinactive material and which issubjected to rubbing treatment or subjected to no alignment treatment.

Based on the studies by the present inventors, the reason why it issuitable to combine an alignment film formed from a photoactive materialand the PS step is as follows. FIG. 8 is a schematic view showing forcomparison the state of polymerization of a polymerizable monomer whenan alignment film formed from a photoinactive material is subjected to aPS step. FIG. 9 is a schematic view showing for comparison the state ofpolymerization of a polymerizable monomer when an alignment film formedfrom a photoactive material is subjected to a PS step. As shown in FIG.8 and FIG. 9, the PS step includes: irradiating a pair of substrates anda liquid crystal composition filled into between the pair of substrateswith light (e.g. ultraviolet light) so as to initiate chainpolymerization (e.g. radical polymerization) of a polymerizable monomer33 or 43 in the liquid crystal layer; and depositing the formed polymeron a surface of an alignment film 32 or 42 at the side of a liquidcrystal layer 30 to form a polymer layer (hereinafter, also referred toas a PS layer) for controlling the alignment of the liquid crystalmolecules.

With a photoinactive alignment film 42, as shown in FIG. 8,polymerizable monomers 43 a which are to be excited by light irradiationare uniformly generated in the liquid crystal layer 30. Excitedpolymerizable monomers 43 b are photo-polymerized to form a polymerlayer at the interface between the alignment film 42 and the liquidcrystal layer 30 owing to phase separation. Thus, the PS step includesmovement of the excited polymerizable monomers 43 b in the bulk towardthe interface between the alignment film 42 and the liquid crystal layer30 after photo-polymerization.

On the other hand, with a photoactive alignment film 32, as shown inFIG. 9, a larger number of excited polymerizable monomers 33 b areformed. This is because the alignment film 32 absorbs the light appliedand the excitation energy thereof is transferred to polymerizablemonomers 33 a. The polymerizable monomers 33 a near the alignment film32 are likely to become excited polymerizable monomers 33 b owing to theexcitation energy. In other words, a larger number of polymerizablemonomers 33 a which are to be excited by light irradiation in the liquidcrystal layer are unevenly distributed near the interface between thealignment film 32 and the liquid crystal layer 30. Thus, with such aphotoactive alignment film 32, the movement of the excited polymerizablemonomers 33 b toward the interface between the alignment film 32 and theliquid crystal layer 30 occurs in a negligible level afterphoto-polymerization. This increases the rates of polymerization and offorming a polymer layer, resulting in formation of a PS layer having astable alignment-regulating force.

The present inventors have studied to have found that the PS layer showsthe effect of suppressing image sticking better for horizontal alignmentfilms than for vertical alignment films. This is presumably because asfollows. FIG. 10 is a schematic view showing the state of polymerizing apolymerizable monomer onto a vertical alignment film. FIG. 11 is aschematic view showing the state of polymerizing a polymerizable monomeronto a horizontal alignment film.

In the case of a vertical alignment film as shown in FIG. 10,photoactive groups 52 included in the vertical alignment film are inindirect contact with liquid crystal molecules 54 and polymerizablemonomers 53 via hydrophobic groups 55. Thus, the excitation energy isless likely to be delivered from the photoactive groups 52 to thepolymerizable monomers 53.

On the other hand, in the case of a horizontal alignment film as shownin FIG. 11, photoactive groups 62 included in the horizontal alignmentfilm are in direct contact with liquid crystal molecules 64 andpolymerizable monomers 63. Thus, the excitation energy is easilydelivered from the photoactive groups 62 to the polymerizable monomers63. This increases the rates of polymerization and of forming a polymerlayer, resulting in formation of a PS layer having a stablealignment-regulating force.

Therefore, the PS step is capable of more markedly improving theefficiency of delivering the excitation energy and of more greatlysuppressing image sticking when performed on an alignment film which isformed from a photoactive material and which is a horizontal alignmentfilm.

As is evident from the above description, what is essential forimproving the rate of forming a PS layer and suppressing image stickingis not to perform photo-alignment treatment but to use a photoactivematerial. Further, what is essential for delivering the excitationenergy between the alignment film and the polymerizable monomer is notphotoisomerization and photocross-linking, which are mechanisms ofphoto-alignment, but photoexcitability.

However, the present inventors have further studied to have focused ondisplay unevenness at the periphery of the display area along a sealingmaterial for bonding the substrates of a liquid crystal display panel inthe case of the PS treatment on a horizontal alignment film formed froma photoactive material. FIG. 12 is a photograph showing displayunevenness at the periphery of the display area in a liquid crystaldisplay panel. A sealing material is applied along the outer edge of thesubstrate, and thus display unevenness occurs along the periphery of thedisplay area. Such display unevenness does not occur, for example, inthe case where the PS treatment is performed on a vertical alignmentfilm or in the case where the PS treatment is not performed and simply ahorizontal alignment film is formed from a photoactive material, butuniquely occurs in the case where the PS treatment is performed on ahorizontal alignment film formed from a photoactive material. This ispresumably attributed to the difference in reactivity to the PSpolymerization. A horizontal alignment film formed from a photoactivematerial has very high reactivity to the PS step, and thus thepolymerization may possibly proceed due to a factor other than the PSstep.

The present invention is devised in view of such a current situation,and it aims to provide a method for manufacturing a liquid crystaldisplay device capable of suppressing display unevenness around a sealin the case of performing PS treatment on a horizontal alignment filmformed from a photoactive material.

Solution to Problem

Various studies by the present inventors have proved that such displayunevenness along the periphery of the display area is caused as follows.When a sealing material is preliminarily applied to one of thesubstrates, a liquid crystal material is dropped on the substrate by aliquid crystal dropping (one drop fill (ODF)) step, and then ultravioletlight is applied for the purpose of seal curing, this ultraviolet lightleaks to the display area (active area) and the monomer in the liquidcrystal layer starts to react, thereby immobilizing the flow alignmentof the liquid crystal. As mentioned above, the system using apolymerizable monomer with a horizontal alignment film formed from aphoto-alignment material shows very high reactivity. Thus, even a slightamount of light leaked to the active area initiates the polymerizationof the monomer even though the active area is covered with a mask so asto be shielded from the ultraviolet light as well as possible.

The present inventors have performed studies on this problem, and thushave found the following: that is, it is effective as the PS step toinitiate polymerization by light irradiation, and use of a materialwhich is curable by irradiation of light whose wavelength is longer thanthe absorption wavelength of the monomer or use of a thermosettingmaterial as a sealing material suppresses display unevenness around thedisplay area due to light irradiation for the purpose of seal curing. Inaddition, they have found that unevenness around the display area can bemore suppressed by adjusting the monomer concentration in the liquidcrystal composition within a range capable of suppressing image stickingand by shielding the display area from light (masking the display area)during light exposure.

The present inventors have furthermore found that not a liquid crystaldropping step (ODF) but a vacuum-injecting step where a liquid crystalcomposition is injected after seal curing enables to suppress displayunevenness around the display area even after light irradiation for thepurpose of seal curing.

The present inventors have thereby arrived at the solution to theproblems and completed the present invention.

In other words, one aspect of the present invention (hereinafter, alsoreferred to as a first manufacturing method of the present invention)relates to a method for manufacturing a liquid crystal display device,including the steps of: forming a horizontal alignment film containing aphotoactive material on at least one substrate of a pair of substrates;dropping a liquid crystal composition containing a liquid crystalmaterial and a monomer on one substrate of the pair of substrates, themonomer being contained in an amount of 1.0% by weight or less in thewhole liquid crystal composition; curing a sealing material applied toone substrate of the pair of substrates along an outer edge thereof byirradiating the sealing material with light whose wavelength is 40 nm ormore longer than an absorption wavelength edge of the monomer; andforming a polymer layer that controls the alignment of liquid crystalmolecules adjacent thereto on the horizontal alignment film byirradiating the liquid crystal composition sealed between the pair ofsubstrates with light to polymerize the monomer.

Another aspect of the present invention (hereinafter, also referred toas a second manufacturing method of the present invention) relates to amethod for manufacturing a liquid crystal display device, including thesteps of: forming a horizontal alignment film containing a photoactivematerial on at least one substrate of a pair of substrates; dropping aliquid crystal composition containing a liquid crystal material and amonomer on one substrate of the pair of substrates; curing a sealingmaterial applied to one substrate of the pair of substrates along anouter edge thereof by heating without light irradiation; and forming apolymer layer that controls the alignment of liquid crystal moleculesadjacent thereto on the horizontal alignment film by irradiating theliquid crystal composition sealed between the pair of substrates withlight to polymerize the monomer.

Another aspect of the present invention (hereinafter, also referred toas a third manufacturing method of the present invention) relates to amethod for manufacturing a liquid crystal display device, including thesteps of: forming a horizontal alignment film containing a photoactivematerial on at least one substrate of a pair of substrates; applying asealing material onto one substrate of the pair of substrates along anouter edge thereof;

bonding the pair of substrates; curing the sealing material;vacuum-injecting a liquid crystal composition containing a liquidcrystal material and a monomer into between the pair of substrates; andforming a polymer layer that controls the alignment of liquid crystalmolecules adjacent thereto on the horizontal alignment film byirradiating the liquid crystal composition sealed between the pair ofsubstrates with light to polymerize the monomer.

Another aspect of the present invention (hereinafter, also referred toas a fourth manufacturing method of the present invention) relates to amethod for manufacturing a liquid crystal display device, including thesteps of: forming a horizontal alignment film containing a photoactivematerial on at least one substrate of a pair of substrates; dropping aliquid crystal composition containing a liquid crystal material and amonomer on one substrate of the pair of substrates, the monomer beingcontained in an amount of 0.4% by weight or less in the whole liquidcrystal composition; curing a sealing material applied to one substrateof the pair of substrates along an outer edge thereof by irradiating thesealing material with light whose wavelength is 10 nm or more longerthan an absorption wavelength edge of the monomer while shielding adisplay area from the light; and forming a polymer layer that controlsthe alignment of liquid crystal molecules adjacent thereto on thehorizontal alignment film by irradiating the liquid crystal compositionsealed between the pair of substrates with light to polymerize themonomer.

The configuration of the method for manufacturing a liquid crystaldisplay device of the present invention is not especially limited byother components as long as it essentially includes such components. Thefollowing will specifically describe the method for manufacturing aliquid crystal display device and preferable modes thereof. Anycombinations of two or more of the following modes of the method formanufacturing a liquid crystal display device are also preferable modesof the method for manufacturing a liquid crystal display device.

The first to fourth manufacturing methods of the present inventioninclude the step of forming a horizontal alignment film containing aphotoactive material on at least one substrate of a pair of substrates.It is preferable to form a horizontal alignment film containing aphotoactive material on each of the pair of substrates. The horizontalalignment film is a film for aligning the liquid crystal moleculesadjacent thereto substantially horizontally to the surface of thehorizontal alignment film. The excitation energy generated during lightapplication onto a photoactive material is more efficiently deliveredfrom a horizontal alignment film to a monomer than from a verticalalignment film to a monomer. Thus, a horizontal alignment film enablesto form a PS layer having a more stable alignment-regulating force.

In such a case, the alignment mode of the liquid crystal display deviceproduced by each of the manufacturing methods is preferably one of anIPS mode, an FFS mode, an optically compensated bend (OCB) mode, atwisted nematic (TN) mode, a super twisted nematic (STN) mode, aferroelectrics liquid crystal (FLC) mode, a polymer dispersed liquidcrystal (PDLC) mode, or a polymer network liquid crystal (PNLC) mode,each of which can utilize a horizontal alignment film. Preferred are theIPS mode and the FFS mode; these modes are easily performed and areexcellent in mass productivity because only one operation of applyingpolarized light from the front side of the substrate can provide desiredalignment. In particular, a liquid crystal display device of the FFSmode includes a plate-like electrode (plate electrode) in addition toslitted electrodes. In the case of bonding the substrates using anelectrostatic chuck, for example, the plate electrode serves as ablocking wall for preventing a high voltage from being applied to theliquid crystal layer. Thus, the FFS mode particularly excellentlyimproves the efficiency of production process.

The above alignment mode is also preferably applied to a structure inwhich a multi-domain structure is formed on at least one of the pair ofsubstrates for the purpose of improving the viewing anglecharacteristic. The multi-domain structure is a structure that includesmultiple regions with different alignment modes (for example, benddirections in the OCB mode or twist directions in the TN and STN modes)or alignment directions of the liquid crystal molecules when no voltageis applied or a voltage is applied, or both of them. Formation of amulti-domain structure requires, for example, patterning of electrodeinto an appropriate shape or using a photomask during application oflight to a photoactive material, or both of such treatments, in apositive manner.

The horizontal alignment film contains a photoactive material. Aphotoactive material in the horizontal alignment film material leads toexcitation of a base material during photopolymerization of a monomer,for example, so that the excitation energy or a radical moves to themonomer. This improves the reactivity in formation of a PS layer.Further, the horizontal alignment film may be subjected tophoto-alignment treatment; in other words, it may be irradiated withlight in certain conditions to achieve alignment characteristics.Hereinafter, a polymer film having an ability to control the alignmentof the liquid crystal by photo-alignment treatment is also referred toas a photo-alignment film.

Examples of the photoactive material include photochromic compoundmaterials, coloring materials, fluorescent materials, phosphorescentmaterials, and photo-alignment film materials. The photoactive materialpreferably contains at least one chemical structure selected from thegroup consisting of terphenyl derivatives, naphthalene derivatives,phenanthrene derivatives, tetracene derivatives, spiropyran derivatives,spiroperimidine derivatives, viologen derivatives, diarylethenederivatives, anthraquinone derivatives, azobenzene derivatives,cinnamoyl derivatives, chalcone derivatives, cinnamate derivatives,coumarin derivatives, stilbene derivatives, and anthracene derivatives.The benzene ring in each of these derivatives may be a heterocyclicring. The term “derivative” herein means a compound substituted by acertain atom or functional group, and a compound introduced as amonovalent functional group, or even as a divalent or polyvalentfunctional group, into the molecular structure. Such derivatives may bein the molecular structure of the polymer main chain or may be in themolecular structure of the polymer side chain, and may be monomers ormay be oligomers. In the case where a horizontal alignment film materialcontains such a monomer or oligomer including a photoactive functionalgroup (preferably in an amount of 3% by weight or more), the polymeritself constituting the horizontal alignment film may be photoinactive.The polymer constituting the horizontal alignment film is preferably apolysiloxane, a polyamide acid, or a polyimide from the viewpoint ofheat resistance. The polymer constituting the horizontal alignment filmmay contain a cyclobutane skeleton.

The photoactive material is more preferably a photo-alignment filmmaterial. The photo-alignment film is a polymer film that generatesanisotropy thereon by polarized or unpolarized light irradiation and hasan ability to give an alignment-regulating force to the liquid crystal.The photo-alignment film material having the aforementioned propertiesmay be a single polymer or may be a mixture with another molecule. Forexample, the photo-alignment film material may contain a polymerincluding a photo-alignable functional group in admixture with a lowmolecular weight molecule such as additives and other photoinactivepolymers. For example, the photo-alignment film material may contain aphotoinactive polymer in admixture with an additive including aphoto-alignable functional group. The photo-alignment film material isselected from materials causing any of photodissociation,photoisomerization, and photodimerization. In comparison withphotodissociation, photoisomerization and photodimerization usuallyallow for alignment with light having a longer wavelength in a lowerexposure dose. Thus, they are excellent in mass productivity.Representative materials causing photodissociation are materialsincluding a compound containing a cyclobutane skeleton.

In other words, the material forming the photo-alignment film preferablyincludes a compound containing either one of or both of aphotoisomerizable functional group and a photodimerizable functionalgroup. Representative materials causing photoisomerization orphotodimerization are azobenzene derivatives, cinnamoyl derivatives,chalcone derivatives, cinnamate derivatives, coumarin derivatives,diarylethene derivatives, stilbene derivatives, and anthracenederivatives.

The photoisomerizable or photodimerizable functional group is morepreferably a cinnamate group or a derivative thereof. These functionalgroups are especially excellent in reactivity. The benzene ring in eachof these functional groups may be a heterocyclic ring.

The horizontal alignment film is preferably a photo-alignment film onwhich photo-alignment treatment is performed by ultraviolet light,visible light, or both of them. Since the PS layer immobilizes thealignment of the liquid crystal, the liquid crystal layer requires noshielding from ultraviolet light or visible light after productionprocess. Thus, the production process can be selected from a wide rangeof choice. The horizontal alignment film is preferably a photo-alignmentfilm on which photo-alignment treatment is performed by polarized orunpolarized light. The alignment-regulating force of the horizontalalignment film mainly depends on the type of the photo-alignment filmmaterial (photofunctional group), and the alignment azimuth, the degreeof pre-tilt angle, and other properties of the liquid crystal moleculesmay be adjusted depending on the type of light, the period of time oflight irradiation, light irradiation intensity, the type of aphotofunctional group, and other factors.

The first manufacturing method of the present invention includes thesteps of: dropping a liquid crystal composition containing a liquidcrystal material and a monomer on one substrate of the pair ofsubstrates, the monomer being contained in an amount of 1.0% by weightor less in the whole liquid crystal composition; and curing a sealingmaterial applied to one substrate of the pair of substrates along anouter edge thereof by irradiating the sealing material with light whosewavelength is 40 nm or more longer than an absorption wavelength edge ofthe monomer. Irradiation with light whose wavelength is longer than theabsorption wavelength edge of the monomer suppresses the polymerizationof the monomer, the polymerization of which is to be initiated byultraviolet light, and suppresses display unevenness generated along theouter edge of the display area in the step of curing the sealingmaterial. The term “absorption wavelength edge” herein means awavelength at an edge of the absorption wavelength range of a monomer.Specifically, it means a wavelength at which the absorbance(absorbance/cm) is 0.01 or lower, where the absorbance is measured witha diluted solution of a target monomer in chloroform at a concentrationof 1.4×10⁻⁴ mol/L and light with an optical path length of 10 mm. Theabsorption wavelength edge of a monomer can be determined by using aUV-VIS absorption spectrum measurement device V7100 (manufactured byJASCO Corp.), for example.

The reason why the light whose wavelength is 40 nm or more longer thanthe absorption wavelength edge of the monomer is applied in the firstmanufacturing method of the present invention is that light having awavelength of the absorption wavelength edge of the monomer or lighthaving a wavelength slightly longer than the absorption wavelength edgemay promote polymerization. This will be specifically described in theevaluation test to be mentioned later.

The second manufacturing method of the present invention includes thesteps of: dropping a liquid crystal composition containing a liquidcrystal material and a monomer on one substrate of the pair ofsubstrates; and curing a sealing material applied to one substrate ofthe pair of substrates along an outer edge thereof by heating withoutlight irradiation. Application of heat suppresses the polymerization ofthe monomer, the polymerization of which is to be initiated by light,and suppresses display unevenness generated along the outer edge of thedisplay area in the step of curing the sealing material. The secondmanufacturing method of the present invention requires a PS monomerwhich is not sufficiently polymerized by heat.

In the first and second manufacturing methods of the present invention,the liquid crystal layer is formed between the pair of substrates by aliquid crystal dropping (ODF) method. Thus, only bonding the pair ofsubstrates as the following step leads to completion of filling theliquid crystal material. Unlike the vacuum injection method to bementioned later, the ODF method requires no inlet for filling the liquidcrystal material.

The third manufacturing method of the present invention includes thesteps of: applying a sealing material onto one substrate of the pair ofsubstrates along an outer edge thereof; bonding the pair of substrates;curing the sealing material; and vacuum-injecting a liquid crystalcomposition containing a liquid crystal material and a monomer intobetween the pair of substrates. In other words, in the thirdmanufacturing method of the present invention, the liquid crystalmaterial is filled into between the pair of substrates by a vacuuminjection method. The method is preferably a dip method. The dip methodis a method in which a pair of substrates bonded by using a sealingmaterial is placed on a dish filled with a liquid crystal material invacuo, and then the pressure is adjusted to an atmospheric pressure, sothat the liquid crystal material is filled into between the pair ofsubstrates owing to the difference between the inner and outer pressuresand a capillary phenomenon. Thereby, the liquid crystal material can befilled after the components of the liquid crystal display panel areassembled except the liquid crystal layer, and disadvantageousproceeding of the PS step does not naturally occur by light irradiationfor the purpose of curing the sealing material.

The fourth manufacturing method of the present invention includes thesteps of: dropping a liquid crystal composition containing a liquidcrystal material and a monomer on one substrate of the pair ofsubstrates, the monomer being contained in an amount of 0.4% by weightor less in the whole liquid crystal composition; and curing a sealingmaterial applied to one substrate of the pair of substrates along anouter edge thereof by irradiating the sealing material with light whosewavelength is 10 nm or more longer than the absorption wavelength edgeof the monomer while shielding the display area from the light. Incomparison with the first manufacturing method of the present invention,the concentration of the monomer in the liquid crystal composition islower and the display area is shielded from light during lightapplication. Thereby, the fourth manufacturing method suppresses displayunevenness generated along the outer edge of the display area eventhough the sealing material is cured by light having a shorterwavelength. In this case, only one of reducing the monomer concentrationand shielding the display area from light fails to give a sufficienteffect. This manufacturing method shows secondary effects of increasingthe degree of curing of the sealing material to improve the peelingstrength and of shortening the cycle time because curing of the seal isfinished with a low exposure dose.

The first to fourth manufacturing methods of the present invention eachinclude the step of forming a polymer layer that controls the alignmentof liquid crystal molecules adjacent thereto on the horizontal alignmentfilm by irradiating the liquid crystal composition sealed between thepair of substrates with light to polymerize the monomer. Since theaforementioned structures suppress the polymerization of the monomer,which is initiated by light irradiation during the step of curing thesealing material, a polymer layer is formed without display unevenness.

The polymer layer is formed by polymerization of a monomer contained inthe liquid crystal composition, and it controls the alignment of theliquid crystal molecules adjacent to the polymer layer. The monomerstarts to polymerize by light irradiation, thereby forming a polymerlayer. The polymerizable functional group of the monomer is preferablyan acrylate group, a methacrylate group, a vinyl group, or a vinyloxygroup. Particularly preferred is an acrylate group or a methacrylategroup. An acrylate group and a methacrylate group generate radicals withhigh probability, and thus are effective for shortening the cycle timein production. The monomer preferably has two or more polymerizablefunctional groups. The more the number of polymerizable functionalgroups is, the higher the reaction efficiency is. Thereby,photopolymerization is achieved in a shorter time. If the monomer hastoo many polymerizable functional groups, the molecular weight becomesso high that the monomer is less likely to dissolve in the liquidcrystal. Thus, the number of polymerizable functional groups in themonomer is more preferably four or less.

The PS layer may be formed by any polymerization in the presentinvention, and examples of the polymerization include “step-growthpolymerization” where bifunctional monomers form new bonds so that themolecular weight increases stepwise, and “chain polymerization” wheremonomers bind to active species generated from a small amount of acatalyst (initiator) one after another so that the polymer sequentiallygrows. Examples of the step-growth polymerization includepolycondensation and polyaddition. Examples of the chain polymerizationinclude radical polymerization and ionic polymerization (e.g. anionicpolymerization, cationic polymerization).

With a horizontal alignment film which is a photo-alignment film, lightfor forming a PS layer, in other words, light used in the step offorming a polymer layer that controls the alignment of liquid crystalmolecules adjacent thereto on the horizontal alignment film bypolymerizing the monomer, is preferably linearly polarized light. Thisis presumably because the light for curing the sealing material affectsthe photo-alignment film, deteriorating the alignment performance of thefilm. Use of linearly polarized light for forming a PS layer after thestep of curing a sealing material improves the alignment performance ofthe liquid crystal adjacent to both of the photo-alignment film and thepolymer layer, resulting in improvement of the contrast ratio.

The polymer layer formed on a horizontal alignment film improves thealignment-regulating force of the horizontal alignment film. Thisgreatly suppresses image sticking and highly improves the displayquality. In the case where a voltage equal to or higher than thethreshold value is applied to the liquid crystal layer formed by theliquid crystal composition and the monomer is polymerized while theliquid crystal molecules are aligned with pre-tilt angle to form apolymer layer, the resulting polymer layer is formed in a state ofhaving a structure to align the liquid crystal molecules with pre-tiltangle.

The electrode is preferably a transparent electrode. Examples of such anelectrode material include transparent materials such as indium tinoxide (ITO) and indium zinc oxide (IZO). This is because as follows. Inthe case where one of a pair of substrates includes a color filter,light for polymerizing a monomer is required to be applied from the sideof the substrate including no color filter. If the electrode of thesubstrate with no color filter blocks light, the monomer isinsufficiently polymerized.

The liquid crystal composition preferably contains liquid crystalmolecules including a multiple bond other than conjugated double bondsof a benzene ring in a molecular structure thereof. A functional groupincluding a multiple bond, such as an alkenyl group, in the molecularstructure of the liquid crystal material more accelerates the PS step.This is presumably because, first, the multiple bond of each liquidcrystal molecule itself can be activated by light, and second, themultiple bond can serve as a transporter (carrier) which is capable ofdelivering the activation energy, radicals, or the like. In other words,not only the use of a photoactive material for a horizontal alignmentfilm but also the use of a liquid crystal which is photoactive or whichserves as a transporter (carrier) for delivering radicals or the likefurther increase the rates of the reaction of a polymerizable monomerand of formation of a PS layer, thereby providing a stable PS layer. Theliquid crystal molecules may be those having positive anisotropy ofdielectric constant (positive liquid crystal molecules) or may be thosehaving negative anisotropy of dielectric constant (negative liquidcrystal molecules). The liquid crystal molecules are preferably nematicliquid crystal molecules having high symmetry in the liquid crystallayer. Examples of the molecular skeleton of the liquid crystalmolecules include a structure including two rings and a group linearlybonding to the ring. The multiple bond excludes the conjugated doublebonds of a benzene ring. This is because the benzene ring is poor inreactivity. The liquid crystal molecules may include the conjugateddouble bonds of a benzene ring as long as it essentially includes amultiple bond other than the conjugated double bonds of a benzene ring.Such bonds are not especially excluded. The liquid crystal compositionmay be a mixture of multiple compositions. The liquid crystalcomposition may be a mixture of multiple kinds of liquid crystalmolecules in order to secure the reliability, to improve the responserate, and to adjust the temperature range of the liquid crystal phase,the elastic constant, the anisotropy of dielectric constant, and therefractive index anisotropy.

The multiple bond is preferably a double bond, and preferably is presentin an ester group or an alkenyl group. For the multiple bonds, a doublebond has better reactivity than a triple bond. The multiple bond may bea triple bond; if this is the case, the triple bond preferably ispresent in a cyano group. Further, the liquid crystal moleculespreferably include two or more kinds of multiple bonds.

The liquid crystal molecules preferably include at least one molecularstructure selected from the group consisting of the structuresrepresented by the following formulae (1-1) to (1-6). The liquid crystalmolecules particularly preferably include the molecular structurerepresented by the following formula (1-4).

Advantageous Effects of Invention

The present invention suppresses polymerization of a monomer in a liquidcrystal composition due to curing of a sealing material, and thusprovides a liquid crystal display device which suffers no displayunevenness along the portion where the sealing material is formed andwhich suffers less deterioration, such as image sticking, of the displayquality.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a liquid crystaldisplay device produced by a method for manufacturing a liquid crystaldisplay device of any of Examples 1 to 12, before a PS polymerizationstep.

FIG. 2 is a schematic cross-sectional view showing a liquid crystaldisplay device produced by a method for manufacturing a liquid crystaldisplay device of any of Examples 1 to 12, after a PS polymerizationstep.

FIG. 3 is a schematic plan view showing a substrate provided withslitted electrodes of Example 1.

FIG. 4 is a graph showing the absorption spectra of the compoundrepresented by the formula (5) below and the compound represented by theformula (6) below.

FIG. 5 is a graph showing that an absorption wavelength of a monomerdissolved in a liquid crystal differs from that of a monomer dissolvedin a solvent such as chloroform.

FIG. 6 is a schematic view showing the state of image sticking in aliquid crystal cell of an IPS mode produced with photo-alignmenttreatment.

FIG. 7 is a schematic view showing the state of image sticking in aliquid crystal cell of an IPS mode produced with photo-alignmenttreatment and a PS step.

FIG. 8 is a schematic view showing for comparison the state ofpolymerization of a polymerizable monomer when an alignment film formedfrom a photoinactive material is subjected to a PS step.

FIG. 9 is a schematic view showing for comparison the state ofpolymerization of a polymerizable monomer when an alignment film formedfrom a photoactive material is subjected to a PS step.

FIG. 10 is a schematic view showing the state of polymerizing apolymerizable monomer onto a vertical alignment film.

FIG. 11 is a schematic view showing the state of polymerizing apolymerizable monomer onto a horizontal alignment film.

FIG. 12 is a photograph showing display unevenness at the periphery ofthe display area in a liquid crystal display panel.

DESCRIPTION OF EMBODIMENTS

The following will describe the method for manufacturing a liquidcrystal display device of the present invention referring to, but notlimited to, examples with reference to the drawings.

First described is a general structure of a liquid crystal displaydevice produced by a method for manufacturing a liquid crystal displaydevice of any of Examples 1 to 12.

The liquid crystal display device produced by the method formanufacturing a liquid crystal display device of any of Examples 1 to 12is a display device including a liquid crystal cell. Such a liquidcrystal display device is suitably used for TV panels, digital signage,medical monitors, electronic books, PC monitors, display panels fortablet devices, display panels for mobile phones, and the like.

FIG. 1 and FIG. 2 each are a schematic cross-sectional view showing aliquid crystal display device produced by a method for manufacturing aliquid crystal display device of any of Examples 1 to 12. FIG. 1 showsthe state before a PS polymerization step, whereas FIG. 2 shows thestate after a PS polymerization step. The liquid crystal display deviceincludes an array substrate 10, a color filter substrate 20, and aliquid crystal layer 30 interposed between a pair of substrates (i.e.the array substrate 10 and the color filter substrate 20). The arraysubstrate 10 includes an insulating transparent substrate 11 formed fromglass, for example, and further includes various components such aswiring, pixel electrodes, a common electrode, and TFTs disposed on thetransparent substrate 11. The color filter substrate 20 includes aninsulating transparent substrate 21 formed from glass, for example, andfurther includes various components such as a color filter and a blackmatrix disposed on the transparent substrate 21. In the case of the IPSmode, for example, electrodes are formed only on the array substrate 10.In the case of other modes, electrodes may optionally be formed on bothof the array substrate 10 and the color filter substrate 20.

The array substrate 10 includes a horizontal alignment film 12, and thecolor filter substrate 20 also includes a horizontal alignment film 22.The horizontal alignment films 12 and 22 each are a film mainlycontaining such components as polyimide, polyamide, polyvinyl, andpolysiloxane. The horizontal alignment films align the liquid crystalmolecules adjacent thereto substantially horizontally to the surfaces ofthe horizontal alignment films. The horizontal alignment films 12 and 22each contain a photoactive material which is, for example, a materialincluding a compound containing the aforementioned photoactivefunctional group.

As shown in FIG. 1, the liquid crystal layer 30 before the PSpolymerization step includes a polymerizable monomer 3 therein. The PSpolymerization step initiates polymerization of the polymerizablemonomer 3. As shown in FIG. 2, the monomer is then formed into PS layers13 and 23 on the horizontal alignment films 12 and 22, respectively,thereby improving the alignment-regulating force of the horizontalalignment films 12 and 22. The polymerizable monomer 3 may be a mixtureof multiple monomers.

The PS layers 13 and 23 may be formed by filling a liquid crystalcomposition containing a liquid crystal material and a polymerizablemonomer into between the array substrate 10 and the color filtersubstrate 20; irradiating the liquid crystal layer 30 with a certainamount of light; and thereby polymerizing the polymerizable monomer 3.Polymerization while applying a voltage equal to or higher than thethreshold value to the liquid crystal layer 30 forms PS layers 13 and 23each having a shape along the initial inclination of the liquid crystalmolecules. In other words, the PS layers 13 and 23 formed have higheralignment stability. The liquid crystal composition may optionallycontain a polymerization initiator.

The polymerizable monomer 3 to be used in Examples 1 to 12 may be amonomer including a monofunctional or polyfunctional polymerizable groupcontaining a ring structure or a mixture of such monomers. Examples ofsuch a monomer include a compound of the chemical formula (2):

[Chem. 2]

P¹—S_(p) ¹—R²-A¹-(Z-A²)_(n)R¹  (2)

in the formula, R¹ represents a —R²-Sp¹-P¹ group, a hydrogen atom, ahalogen atom, a —CN group, an —NO₂ group, an —NCO group, an —NCS group,an —OCN group, an —SCN group, an —SF₅ group, or a C1 to C12 linear orbranched alkyl group;

P¹ represents a polymerizable group;

Sp¹ represents a C1 to C6 linear, branched, or cyclic alkylene oralkyleneoxy group, or a direct bond;

a hydrogen atom in R¹ may be substituted with a fluorine atom or achlorine atom;

a —CH₂— group in R¹ may be substituted with an —O— group, an —S— group,an —NH— group, a —CO— group, a —COO— group, an —OCO— group, an —O—COO—group, an —OCH₂— group, a —CH₂O— group, an —SCH₂— group, a —CH₂S— group,an —N(CH₃)— group, an —N(C₂H₅)— group, an —N(C₃H₇)— group, an —N(C₄H₉)—group, a —CF₂O— group, an —OCF₂— group, a —CF₂S— group, an —SCF₂— group,an —N(CF₃)— group, a —CH₂CH₂— group, a —CF₂CH₂— group, a —CH₂CF₂— group,a —CF₂CF₂— group, a —CH═CH— group, a —CF═CF— group, a —C≡C— group, a—CH═CH—COO— group, or an —OCO—CH═CH— group as long as an oxygen atom anda sulfur atom are not adjacent to each other;

R² represents an —O— group, an —S— group, an —NH— group, a —CO— group, a—COO— group, an —OCO— group, an —O—COO— group, an —OCH₂— group, a —CH₂O—group, an —SCH₂— group, a —CH₂S— group, an —N(CH₃)— group, an —N(C₂H₅)—group, an —N(C₃H₇)— group, an —N(C₄H₉)— group, a —CF₂O— group, an —OCF₂—group, a —CF₂S— group, an —SCF₂— group, an —N(CF₃)— group, a —CH₂CH₂—group, a —CF₂CH₂— group, a —CH₂CF₂— group, a —CF₂CF₂— group, a —CH═CH—group, a —CF═CF— group, a —C≡C— group, a —CH═CH—COO— group, an—OCO—CH═CH— group, or a direct bond;

A¹ and A² are the same as or different from each other, and eachrepresents a 1,2-phenylene group, a 1,3-phenylene group, a 1,4-phenylenegroup, a naphthalene-1,4-diyl group, a naphthalene-1,5-diyl group, anaphthalene-2,6-diyl group, a 1,4-cyclohexylene group, a1,4-cyclohexenylene group, a 1,4-bicyclo[2.2.2]octylene group, apiperidine-1,4-diyl group, a naphthalene-2,6-diyl group, adecahydronaphthalene-2,6-diyl group, a1,2,3,4-tetrahydronaphthalene-2,6-diyl group, an indan-1,3-diyl group,an indan-1,5-diyl group, an indan-2,5-diyl group, aphenanthrene-1,6-diyl group, a phenanthrene-1,8-diyl group, aphenanthrene-2,7-diyl group, a phenanthrene-3,6-diyl group, ananthracene-1,5-diyl group, an anthracene-1,8-diyl group, ananthracene-2,6-diyl group, or an anthracene-2,7-diyl group;

—CH₂— groups in A¹ and A² each may be substituted with an —O— group oran —S— group as long as they are not adjacent to each other;

hydrogen atoms in A¹ and A² each may be substituted with a fluorineatom, a chlorine atom, a —CN group, or a C1 to C6 alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, or alkylcarbonyloxy group;

Zs are the same as or different from each other, and each represents an—O— group, an —S— group, an —NH— group, a —CO— group, a —COO— group, an—OCO— group, an —O—COO— group, an —OCH₂— group, a —CH₂O— group, an—SCH₂— group, a —CH₂S— group, an —N(CH₃)— group, an —N(C₂H₅)— group, an—N(C₃H₇)— group, an —N(C₄H₉)— group, a —CF₂O— group, an —OCF₂— group, a—CF₂S— group, an —SCF₂— group, an —N(CF₃)— group, a —CH₂CH₂— group, a—CF₂CH₂— group, a —CH₂CF₂— group, a —CF₂CF₂— group, a —CH═CH— group, a—CF═CF— group, a —C≡C— group, a —CH═CH—COO— group, an —OCO—CH═CH— group,or a direct bond; and

n is 0, 1, or 2.

More specific examples thereof include any of compounds represented bythe following chemical formulae (3-1) to (3-5):

in each formula, P¹s are the same as or different from each other, andeach represents a polymerizable group; part or all of hydrogen atoms ofthe benzene rings may be substituted with a halogen atom or a C1 to C12alkyl or alkoxy group; and part or all of hydrogen atoms of the C1 toC12 alkyl or alkoxy group may be substituted with a halogen atom.

The monomers represented by the chemical formulae (3-1) to (3-5) arecompounds that are photocleavable by ultraviolet light irradiation togenerate radicals, and thus the polymerization thereof proceeds withouta polymerization initiator. As a result, such monomers suppressdeterioration of display quality, such as image sticking, due toremaining of a polymerization initiator after completion of the PS step.

Examples of P¹ include an acryloyloxy group, a methacryloyloxy group, avinyl group, a vinyloxy group, an acryloylamino group, and amethacryloylamino group.

The polymerizable monomer 3 to be used in Examples 1 to 12 may be any ofcompounds represented by the following chemical formulae (4-1) to (4-8):

in each formula, R³ and R⁴ are the same as or different from each other,and each represents an -Sp²-P² group, a hydrogen atom, a halogen, a —CNgroup, an —NO₂ group, an —NCO group, an —NCS group, an —OCN group, an—SCN group, an —SF₅ group, or a C1 to C12 linear or branched alkyl,aralkyl, or phenyl group,

at least one of R³ and R⁴ includes an -Sp²-P² group;

P² represents a polymerizable group;

Sp² represents a C1 to C6 linear, branched, or cyclic alkylene oralkyleneoxy group, or a direct bond;

provided that at least one of R³ and R⁴ represents a C1 to C12 linear orbranched alkyl, aralkyl, or phenyl group, a hydrogen atom in the atleast one of R³ and R⁴ may be substituted with a fluorine atom, achlorine atom, or an -Sp²-P² group;

a —CH₂— group in R¹ and R² may be substituted with an —O— group, an —S—group, an —NH— group, a —CO— group, a —COO— group, an —OCO— group, an—O—COO— group, an —OCH₂— group, a —CH₂O— group, an —SCH₂— group, a—CH₂S— group, an —N(CH₃)— group, an —N(C₂H₅)— group, an —N(C₃H₇)— group,an —N(C₄H₉)— group, a —CF₂O— group, an —OCF₂— group, a —CF₂S— group, an—SCF₂— group, an —N(CF₃)— group, a —CH₂CH₂— group, a —CF₂CH₂— group, a—CH₂CF₂— group, a —CF₂CF₂— group, a —CH═CH— group, a —CF═CF— group, a—C≡C— group, a —CH═CH—COO— group, or an —OCO—CH═CH— group as long as anoxygen atom, a sulfur atom, and a nitrogen atom are not adjacent to eachother;

part or all of hydrogen atoms of the benzene rings may be substitutedwith a halogen atom or a C1 to C12 alkyl or alkoxy group; part or all ofhydrogen atoms of the C1 to C12 alkyl or alkoxy group may be substitutedwith a halogen atom.

Examples of P² include an acryloyloxy group, a methacryloyloxy group, avinyl group, a vinyloxy group, an acryloylamino group, and amethacryloylamino group.

The compounds represented by the chemical formulae (4-1) to (4-8) arecompounds that generate radicals by visible light irradiation and theresulting hydrogen abstraction, and thus the polymerization thereofproceeds without a polymerization initiator. As a result, such compoundssuppress deterioration of display quality, such as image sticking, dueto remaining of a polymerization initiator even after completion of thePS step.

A sealing material 81 is disposed between the array substrate 10 and thecolor filter substrate 20 along an outer edge of these substrates. Thesealing material 81 may be a resin curable by light or heat, forexample. The liquid crystal layer 30 is formed by bonding the arraysubstrate 10 and the color filter substrate 20 with the sealing material81 such that the liquid crystal composition is contained between thesubstrates. Since the PS step is performed after bonding by the sealingmaterial, the sealing material 81 is formed on the horizontal alignmentfilms 12 and 22, while the PS layers 13 and 23 are formed in a regionsurrounded by the sealing material 81 as shown in FIG. 2.

In the liquid crystal display device, the array substrate 10, the liquidcrystal layer 30, and the color filter substrate 20 are laminated in thestated order from the back side to the viewing side of the liquidcrystal display device, thereby forming a liquid crystal cell. The backside of the array substrate 10 and the viewing side of the color filtersubstrate 20 each are provided with a linearly polarizing plate. Each ofthese linearly polarizing plates may further be provided with a retarderto form a circularly polarizing plate.

The liquid crystal display device may be of a transmissive type, areflective type, or a transflective type. Transmissive or transflectiveliquid crystal display devices further include a backlight. Thebacklight is disposed on the back side of the liquid crystal cell, andthe light emitted therefrom passes through the array substrate 10, theliquid crystal layer 30, and the color filter substrate 20 in the statedorder. The array substrate 10 of a reflective or transflective liquidcrystal display device includes a reflector for reflecting outsidelight. The polarizing plate on the color filter substrate 20 needs to bea circularly polarizing plate at least in a region utilizing reflectedlight for display.

The liquid crystal display device may be of a color filter on array(COA) type where a color filter is formed on an array substrate or of ablack matrix on array (BOA) type where a black matrix is formed on anarray substrate. The display device may be a monochrome display or afield sequential color display. In these cases, no color filter isrequired.

The liquid crystal layer 30 is filled with a liquid crystal materialthat has a characteristic of aligning in a specific direction inresponse to a certain voltage. The alignment characteristic of theliquid crystal molecules in the liquid crystal layer 30 is controlled byapplication of a voltage equal to or higher than the threshold value.

The sealing material component, the alignment film component, themonomer component in the PS layer, and the like may be analyzed bydisassembling the liquid crystal display device and performing chemicalanalysis utilizing, for example, gas chromatograph mass spectrometry(GC-MS) or time-of-flight secondary ion mass spectrometry (TOF-SIMS).Further, microscopic observation using, for example, a scanningtransmission electron microscope (STEM) or a scanning electronmicroscope (SEM) may show the cross section of the liquid crystal cellincluding the alignment film and the PS layer. In the case of fillingthe liquid crystal by a vacuum injection method, the seal has a patternof an inlet.

The following will describe the methods for manufacturing a liquidcrystal display device of Examples 1 to 12 where liquid crystal displayswere actually manufactured.

Example 1

Example 1 is an example of producing a liquid crystal cell of the FFSmode. Further, Example 1 corresponds to the first manufacturing methodof the present invention. A TFT substrate (FFS substrate) provided withslitted electrodes and a plate-like electrode (plate electrode) and acounter substrate provided with a color filter were prepared, and apolyvinyl cinnamate solution as a material for a horizontal alignmentfilm was applied on each substrate by a spin-coating method. The size ofthe TFT substrate was 10 inches. One of the slitted electrode and theplate electrode served as a signal electrode, and the other served as acommon electrode. FIG. 3 is a schematic plan view showing a substrateprovided with slitted electrodes of Example 1. The double-headed arrowin FIG. 3 indicates the polarization direction of light applied (in thecase of using negative liquid crystal molecules). The materials of theslitted electrodes 71 and the plate electrode 72 each were a transparentmaterial. Each slit 71 a of the slitted electrodes had a V shape; thewidth L of each slit 71 a of the slitted electrodes was 3 μm; and thespacing S between slits 71 a was 5 μm. The polyvinyl cinnamate solutionwas prepared by dissolving polyvinyl cinnamate in a solvent mixture ofthe same amounts of N-methyl-2-pyrrolidone and ethylene glycol monobutylether such that the amount of the polyvinyl cinnamate in the wholesolution was 3% by weight.

The applied materials by a spin-coating method were pre-dried at 100° C.for one minute, and then baked at 220° C. for 40 minutes under nitrogenpurge. The baked alignment film on the slitted electrodes at the displayarea (active area) of the TFT substrate had a thickness of 75 nm. Thebaked alignment film at the display area (active area) of the colorfilter substrate was 85 nm.

Then, photo spacers were formed on the counter substrate to adjust thethickness of the liquid crystal layer at the display area (active area)to 3.5 μm. The bottom diameter of the photo spacer was 12 μm. The bottomdiameter herein is defined by the diameter of the portion in contactwith the layer just below the alignment film.

Next, with respect to the alignment treatment, the surfaces of thesubstrates were irradiated with linearly polarized ultraviolet lightfrom the normal direction of the substrates so as to give a dose of 5J/cm² at a wavelength of 313 nm. The degree of polarization of thelinearly polarized light was 30:1. As shown in FIG. 3, the angle betweenthe longitudinal direction of the slitted electrode and the polarizationdirection was 10°. Thereby, the liquid crystal molecules 74 are alignedin the direction substantially orthogonal to the polarization directionof the linearly polarized ultraviolet light when no voltage is applied,while they are aligned in the direction substantially orthogonal to thelongitudinal direction of the slitted electrode when a voltage equal toor higher than the threshold value is applied.

Next, a heat- and visible-light-curable sealing material (WORLD ROCK,manufactured by Kyoritsu Chemical & Co., Ltd.) was applied on the TFTsubstrate along its outer edge by using a dispenser.

A liquid crystal composition containing a liquid crystal material and amonomer was dropped on the counter substrate. The liquid crystalcomposition was prepared by addingtrans-4-propyl-4′-vinyl-1,1′-bicyclohexane as a liquid crystallinemolecule including an alkenyl group (5% by weight in the whole of theliquid crystal composition) and biphenyl-4,4′-diylbis(2-methyl acrylate)represented by the following chemical formula (5) as a monomer (1.0% byweight in the whole of the liquid crystal composition) to MLC-6610(manufactured by Merck KGaA). The monomer represented by the followingchemical formula (5) is a compound which has an absorption wavelengthedge of 325 nm and which is insufficiently polymerized by light whosewavelength is 365 nm or longer or by heat.

The two substrates were bonded such that the polarization directions ofthe ultraviolet light irradiating the respective substrates correspondedto each other.

The seal was cured by using an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) while pressing the bonded substrates at 0.5kgf/cm². A filter for shielding light having a wavelength of 380 nm orshorter was disposed between the bonded substrates and theultra-high-pressure UV lamp, so that the substrates were not irradiatedwith ultraviolet light.

The workpiece was heated at 130° C. for 40 minutes under pressure tothermal-cure the seal, and to make the liquid crystal molecules have anisotropic phase for realignment treatment. In order to prevent thealignment of the liquid crystal from being disturbed by an externalfield, the electrodes were short-circuited and the surface of the glasssubstrate was subjected to charge elimination.

This provided a liquid crystal cell with alignment orthogonal to thepolarization direction of ultraviolet light irradiating the alignmentfilm and uniaxial alignment in the plane of the substrate.

These steps were performed under a yellow fluorescent lamp, and theliquid crystal cell was shielded from the ultraviolet light emitted fromthe fluorescent lamp. Immediately before the following PS treatment, theliquid crystal cell was heated at 130° C. for 40 minutes so that chargeelimination was elaborately performed.

Next, the liquid crystal cell was irradiated with unpolarizedultraviolet light at a dose of 1.5 J/cm² by using a black light(FHF32BLB, manufactured by TOSHIBA CORP.) for the PS treatment. Thisproceeded the polymerization of biphenyl-4,4′-diylbis(2-methylacrylate). Thereby, a liquid crystal cell of Example 1 was produced.

This liquid crystal cell and other parts were assembled into a liquidcrystal display panel, and its display was visually observed. Theobservation revealed that the display was good without alignmentunevenness and suffered less image sticking.

Example 2

A liquid crystal cell was produced in the same manner as in Example 1except that a different monomer was used. Example 2 corresponds to thefirst manufacturing method of the present invention. Specifically, theliquid crystal composition was prepared by addingtrans-4-propyl-4′-vinyl-1,1′-bicyclohexane as a liquid crystallinemolecule including an alkenyl group (5% by weight in the whole of theliquid crystal composition) and phenanthrene-2,7-diylbis(2-methylacrylate) represented by the following chemical formula (6) as a monomer(1.0% by weight in the whole of the liquid crystal composition) toMLC-6610 (manufactured by Merck KGaA). The monomer represented by thefollowing chemical formula (6) is a compound which has an absorptionwavelength edge of 360 nm and which is insufficiently polymerized bylight whose wavelength is 405 nm or longer or by heat.

This liquid crystal cell and other parts were assembled into a liquidcrystal display panel, and its display was visually observed. Theobservation revealed that the display was good without alignmentunevenness and suffered less image sticking.

FIG. 4 is a graph showing the absorption spectra of the compoundrepresented by the formula (5) and the compound represented by theformula (6). The spectra were measured by using a UV-VIS absorptionspectrum measurement device V7100 (manufactured by JASCO Corp.).

Example 3

In Example 3, a liquid crystal cell was produced in the same manner asin Example 1 except that a thermosetting sealing material (HC1413FP,manufactured by Mitsui Chemicals, Inc.) was used as a sealing materialand ultraviolet light was not applied from an ultra-high-pressure UVlamp for curing the sealing material. Example 3 corresponds to thesecond manufacturing method of the present invention. This liquidcrystal cell and other parts were assembled into a liquid crystaldisplay panel, and its display was visually observed. The observationrevealed that the display was good without alignment unevenness andsuffered less image sticking.

Comparative Example 1

A liquid crystal cell was assembled in the same manner as in Example 3except that a heat- and ultraviolet-light-curable sealing material(Photolec S-WB, manufactured by SEKISUI CHEMICAL CO., LTD.) was used asa sealing material and ultraviolet light was applied by using anultra-high-pressure UV lamp (USH-500D, manufactured by USHIO INC.) forcuring the sealing material without disposing a filter for shieldinglight having a wavelength of 380 nm or shorter. Then, display of theliquid crystal cell was visually observed and the observation revealedthat the display showed alignment unevenness throughout the displayarea.

Comparative Example 2

The same procedure as in Comparative Example 1 was performed except thata chromium-plated silica glass was disposed so as to shield the displayarea from ultraviolet light upon curing the sealing material, and unevenalignment unevenness along the sealing material (the periphery of thedisplay area) was observed as shown in FIG. 12.

Example 4

Example 4 is an example of producing a liquid crystal cell of the FFSmode. Example 4 corresponds to the third manufacturing method of thepresent invention. A TFT substrate (FFS substrate) provided with slittedelectrodes and a plate-like electrode (plate electrode) and a countersubstrate provided with a color filter were prepared, and a polyvinylcinnamate solution as a material for a horizontal alignment film wasapplied on each substrate by a spin-coating method. The size of the TFTsubstrate was 10 inches. The materials of the slitted electrodes 71 andthe plate electrode 72 each were a transparent material. Each slit 71 aof the slitted electrodes had a V shape; the width L of each slit 71 aof the slitted electrodes was 3 μm; and the spacing S between slits 71 awas 5 μm. The polyvinyl cinnamate solution was prepared by dissolvingpolyvinyl cinnamate in a solvent mixture of the same amounts ofN-methyl-2-pyrrolidone and ethylene glycol monobutyl ether such that theamount of the polyvinyl cinnamate in the whole solution was 3% byweight.

The applied materials by a spin-coating method were pre-dried at 100° C.for one minute, and then baked at 220° C. for 40 minutes under nitrogenpurge. The baked alignment film on the slitted electrodes at the displayarea (active area) of the TFT substrate had a thickness of 75 nm. Thebaked alignment film at the display area (active area) of the colorfilter substrate was 85 nm.

Then, photo spacers were formed on the counter substrate to adjust thethickness of the liquid crystal layer at the display area (active area)to 3.5 μm. The bottom diameter of the photo spacer was 12 μm. The bottomdiameter herein is defined by the diameter of the portion in contactwith the layer just below the alignment film.

Next, with respect to the alignment treatment, the surfaces of thesubstrates were irradiated with linearly polarized ultraviolet lightfrom the normal direction of the substrates so as to give a dose of 5J/cm² at a wavelength of 313 nm. The angle between the longitudinaldirection of the slitted electrode and the polarization direction was10°.

Next, a heat- and ultraviolet-light-curable sealing material (PhotolecS-WB, manufactured by SEKISUI CHEMICAL CO., LTD.) was applied on the TFTsubstrate along its outer edge by using a dispenser. The applyingpattern was such that an inlet was partially formed so as to make itpossible to inject the liquid crystal composition during thepost-process.

The two substrates were bonded such that the polarization directions ofthe ultraviolet light irradiating the respective substrates correspondedto each other.

The seal was cured by using an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) while pressing the bonded substrates at 0.5kgf/cm². The workpiece was heated at 130° C. for 40 minutes underpressure to further cure the seal.

Next, a liquid crystal composition containing a liquid crystal materialand a monomer was filled into between the pair of substrates by a vacuuminjection (dip) method. The liquid crystal composition was the same asin Example 1. After the liquid crystal composition was filled, the inletof the cell was sealed with an epoxy-type adhesive (Araldite AR-S30,manufactured by NICHIBAN Co., Ltd.).

Next, in order to remove the flow alignment of the liquid crystal, arealignment treatment of heating the workpiece at 130° C. for 40 minutesto make the liquid crystal molecules have an isotropic phase wasperformed. In order to prevent the alignment of the liquid crystal frombeing disturbed by an external field, the electrodes wereshort-circuited and the surfaces of the glass substrates were subjectedto charge elimination.

This provided a liquid crystal cell with alignment orthogonal to thepolarization direction of ultraviolet light irradiating the alignmentfilm and uniaxial alignment in the plane of the substrate.

These steps were performed under a yellow fluorescent lamp, and theliquid crystal cell was shielded from the ultraviolet light emitted fromthe fluorescent lamp. Immediately before the following PS treatment, theliquid crystal cell was heated at 130° C. for 40 minutes so that chargeelimination was elaborately performed.

Next, the liquid crystal cell was irradiated with ultraviolet light at adose of 1.5 J/cm² by using a black light (FHF32BLB, manufactured byTOSHIBA CORP.) for the PS treatment. This proceeded the polymerizationof biphenyl-4,4′-diylbis(2-methyl acrylate). Thereby, a liquid crystalcell of Example 4 was produced.

This liquid crystal cell and other parts were assembled into a liquidcrystal display panel, and its display was visually observed. Theobservation revealed that the display was good without alignmentunevenness and suffered less image sticking.

Comparative Example 3

A liquid crystal cell was assembled in the same manner as in Example 4(that is, in the same manner as in Comparative Example 1) except thatthe liquid crystal was filled not by a vacuum injection method but bythe liquid crystal dropping method. Then, display of the liquid crystalcell was visually observed and the observation revealed that the displayshowed alignment unevenness along the sealing material (the periphery ofthe display area) as shown in FIG. 12.

Example 5

In Example 5, a liquid crystal cell was produced in the same manner asin Example 1 except that a solution of polyimide including a cyclobutaneskeleton was used as an alignment film material and the alignmenttreatment was performed in different conditions. The alignment filmmaterial was applied to the substrates and dried in the same conditionsas in Example 1. With respect to the alignment treatment, the surfacesof the substrates were irradiated with linearly polarized ultravioletlight from the normal direction of the substrates so as to give a doseof 500 mJ/cm² at a wavelength of 254 nm. This led to photodissociationof the alignment film material applied on the substrates, therebyproviding horizontal alignment films.

A display panel including the liquid crystal cell according to Example 5was evaluated for its performance, resulting in no display unevennessaround the seal, no increase in driving voltage, no decrease incontrast, and no marked deterioration in voltage holding ratio. Further,the display panel had a particularly improved effect against imagesticking.

Evaluation Test 1

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (5) used as the monomer, the following liquidcrystal cells of Reference Examples 1 to 4 were produced and examined.

Reference Example 1

A pair of bare glass substrates with no components such as electrodeswas prepared, and a polyvinyl cinnamate solution as a material forhorizontal alignment films was applied on each substrate by aspin-coating method. The polyvinyl cinnamate solution was prepared bydissolving polyvinyl cinnamate in a solvent mixture of the same amountsof N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether such thatthe amount of the polyvinyl cinnamate in the whole solution was 3% byweight.

The applied materials by a spin-coating method were pre-dried at 90° C.for one minute, and then baked at 220° C. for 60 minutes under nitrogenpurge. The baked alignment films each had a thickness of 100 nm.

Next, with respect to the alignment treatment, the surfaces of thesubstrates were irradiated with linearly polarized ultraviolet lightfrom the normal direction of the substrates so as to give a dose of 5J/cm² at a wavelength of 313 nm.

Next, a thermosetting sealing material (HC1413FP: manufactured by MitsuiChemicals, Inc.) was applied on one substrate along the outer edge ofthe substrate by using a screen printing plate. The applying pattern wassuch that an inlet was partially formed so as to make it possible toinject the liquid crystal composition during the post-process.

Then, beads (SP-2035, manufactured by SEKISUI CHEMICAL CO., LTD.) havinga diameter of 3.5 μm were dispersed on one substrate to adjust thethickness of the liquid crystal layer to 3.5 μm. The two substrates werebonded such that the polarization directions of the ultraviolet lightirradiating the respective substrates corresponded to each other.

The seal was cured by using an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) while pressing the bonded substrates at 0.5kgf/cm². The workpiece was heated at 130° C. for 60 minutes underpressure to further cure the seal.

Next, a liquid crystal composition containing a liquid crystal materialand a monomer was filled into between the pair of substrates by a vacuuminjection method. The liquid crystal composition was prepared by addingtrans-4-propyl-4′-vinyl-1,1′-bicyclohexane as a liquid crystallinemolecule (5% by weight in the whole of the liquid crystal composition)and biphenyl-4,4′-diylbis(2-methyl acrylate) as a monomer (0.3% byweight in the whole of the liquid crystal composition) to MLC-6610(manufactured by Merck KGaA). After the liquid crystal composition wasfilled, the inlet of the cell was sealed with an epoxy-type adhesive(Araldite AR-S30, manufactured by NICHIBAN Co., Ltd.).

In order to prevent the alignment of the liquid crystal from beingdisturbed by an external field, the electrodes were short-circuited andthe surfaces of the glass substrates were subjected to chargeelimination. At this time, the liquid crystal molecules wereflow-aligned.

Next, the whole liquid crystal cell was irradiated with light at a doseof 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D, manufacturedby USHIO INC.) as a light source through a 340-nm band-pass filter.

A realignment treatment of heating the liquid crystal cell of ReferenceExample 1 thus produced at 130° C. for 40 minutes was performed. As aresult, the PS polymerization proceeded in the liquid crystalcomposition to immobilize the alignment of the liquid crystal, and theliquid crystal held the flow alignment.

Reference Example 2

A liquid crystal cell of Reference Example 2 was produced by the samemethod as in Reference Example 1 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 360-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the PS polymerizationproceeded in the liquid crystal composition to immobilize the alignmentof the liquid crystal, and the liquid crystal held the flow alignment.

Reference Example 3

A liquid crystal cell of Reference Example 3 was produced by the samemethod as in Reference Example 1 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 365-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the flow alignment ofthe liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Reference Example 4

A liquid crystal cell of Reference Example 4 was produced by the samemethod as in Reference Example 1 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 370-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the flow alignment ofthe liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 365 nm makes it possible to suppress the polymerization of themonomer represented by the chemical formula (5) at the same time ofcuring the sealing material.

Evaluation Test 2

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (6) used as the monomer, the following liquidcrystal cells of Reference Examples 5 to 8 were produced and examined.

Reference Example 5

A liquid crystal cell of Reference Example 5 was produced by the samemethod as in Reference Example 1 except that the compound represented bythe chemical formula (6) was used as the monomer and the whole liquidcrystal cell was subjected to the PS step such that it was irradiatedwith light at a dose of 2 J/cm² from an ultra-high-pressure UV lamp(USH-500D, manufactured by USHIO INC.) as a light source through a380-nm band-pass filter. A realignment treatment of heating this liquidcrystal cell at 130° C. for 40 minutes was performed. As a result, thePS polymerization proceeded in the liquid crystal composition toimmobilize the alignment of the liquid crystal, and the liquid crystalheld the flow alignment.

Reference Example 6

A liquid crystal cell of Reference Example 6 was produced by the samemethod as in Reference Example 5 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 390-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the PS polymerizationproceeded in the liquid crystal composition to immobilize the alignmentof the liquid crystal, and the liquid crystal held the flow alignment.

Reference Example 7

A liquid crystal cell of Reference Example 7 was produced by the samemethod as in Reference Example 5 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 400-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the flow alignment ofthe liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Reference Example 8

A liquid crystal cell of Reference Example 8 was produced by the samemethod as in Reference Example 5 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 2 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 420-nm band-passfilter. A realignment treatment of heating this liquid crystal cell at130° C. for 40 minutes was performed. As a result, the flow alignment ofthe liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 400 nm makes it possible to suppress the polymerization of themonomer represented by the chemical formula (6) at the same time ofcuring the sealing material.

The following will describe the results of considerations by the presentinventors about the reasons why the reaction of the monomer is proceededby light having a wavelength at the absorption wavelength edge of themonomer. FIG. 5 is a graph showing that an absorption wavelength of amonomer dissolved in a liquid crystal differs from that of a monomerdissolved in a solvent such as chloroform. Based on the comparisonbetween the absorption spectrum of molecules floating in a vacuum or ina solvent and that of molecules in an aggregated state like a solid, theabsorption spectrum of the solid is broader than the other as shown inFIG. 5. This is because the intermolecular interaction is stronger insolid than in liquid. In the above examples, presumably, the monomer isdissolved in the liquid crystal, and the liquid crystal moleculesincluding many polar groups and electrons strongly interact with themonomer. Thus, the monomer may have more various molecular conformationsor electron-excited states. This presumably results in a broaderabsorption spectrum of the monomer in the liquid crystal and elongationof the absorption wavelength edge compared with the case of dissolvingthe monomer in a solvent (e.g. chloroform). The degree of elongation ofthe wavelength is assumed to be about +40 nm based on the results of theEvaluation Tests 1 and 2.

In the case where the seal is cured by light having a wavelength ofabout 40 nm longer than the absorption wavelength edge of the monomer,some kinds of monomer may cause insufficient seal curing. For example,phenanthrene-2,7-diylbis(2-methyl acrylate) represented by the chemicalformula (6) used in Example 2 has an absorption wavelength edge of 360nm, and thus the light for seal curing is visible light. Curing of thesealing material by visible light prolongs the cycle time of curingtreatment. Thus, it is preferable to use light having a wavelength thatis shorter than the absorption wavelength edge+40 nm. In other words,the light for seal curing preferably has a wavelength that is longerthan the absorption wavelength edge of the monomer and is shorter thanthe absorption wavelength edge+40 nm.

The present inventors have performed studies in order to achieve suchimprovement, and have found that a monomer concentration of 1.0% byweight or less and shielding of the display area from light uponirradiation can suppress display unevenness along the outer edge of thedisplay area even though the sealing material is cured by light having ashorter wavelength. This method increases the degree of curing of thesealing material to improve the peeling strength and enables the seal tobe cured at a low dose, thereby decreasing the cycle time. This is thespirit of the fourth manufacturing method of the present invention. Thefollowing will describe examples.

Example 6

The amount of the monomer in the liquid crystal composition was 0.4% byweight in the whole liquid crystal composition, and a filter forshielding light having a wavelength of 335 nm or shorter and achromium-plated silica glass for shielding the display area from lightwere disposed between the bonded substrates and the ultra-high-pressureUV lamp, thereby shielding the display area from ultraviolet light. Theother conditions were the same as those in Example 1.

The liquid crystal cell thereby produced and other parts were assembledinto a liquid crystal display panel, and its display was visuallyobserved. The observation revealed that the display was good withoutalignment unevenness and suffered less image sticking.

Example 7

The same procedure as in Example 1 was performed except that the amountof the monomer in the liquid crystal composition was 0.4% by weight inthe whole liquid crystal composition, the monomer wasphenanthrene-2,7-diylbis(2-methyl acrylate) represented by the formula(6), and a filter for shielding light having a wavelength of 370 nm orshorter and a chromium-plated silica glass for shielding the displayarea from light were disposed between the bonded substrates and theultra-high-pressure UV lamp, thereby shielding the display area fromultraviolet light.

The liquid crystal cell thereby produced and other parts were assembledinto a liquid crystal display panel, and its display was visuallyobserved. The observation revealed that the display was good withoutalignment unevenness and suffered less image sticking.

Evaluation Test 3

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (5) used as the monomer, the following liquidcrystal cells of Reference Examples 9 to 12 were produced and examined.

Reference Example 9

A liquid crystal cell of Reference Example 9 was produced by the samemethod as in Reference Example 1 except that the compound represented bythe chemical formula (5) was used as the monomer, the amount of themonomer in the liquid crystal composition was 0.4% by weight in thewhole liquid crystal composition, and the whole liquid crystal cell wassubjected to the PS step such that it was irradiated with light at adose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 315-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)in the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 10

A liquid crystal cell of Reference Example 10 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 325-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)in the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 11

A liquid crystal cell of Reference Example 11 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 335-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Reference Example 12

A liquid crystal cell of Reference Example 12 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 345-nm band-passfilter with the display area of the liquid crystal cell shielded fromthe light. A realignment treatment of heating this liquid crystal cellat 130° C. for 40 minutes was performed. As a result, the flow alignmentof the liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 335 nm and shielding of the display area of the liquid crystal cellfrom light make it possible to suppress the polymerization of themonomer represented by the chemical formula (5) at the same time ofcuring the sealing material.

Evaluation Test 4

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (6) used as the monomer, the following liquidcrystal cells of Reference Examples 13 to 16 were produced and examined.

Reference Example 13

A liquid crystal cell of Reference Example 13 was produced by the samemethod as in Reference Example 9 except that the compound represented bythe chemical formula (6) was used as the monomer and the whole liquidcrystal cell was subjected to the PS step such that it was irradiatedwith light at a dose of 1 J/cm² from an ultra-high-pressure UV lamp(USH-500D, manufactured by USHIO INC.) as a light source through a350-nm band-pass filter while shielding the display area from the light.A realignment treatment of heating this liquid crystal cell at 130° C.for 40 minutes was performed. As a result, the PS polymerizationproceeded in the region along the sealing material (the outer edge ofthe display area) in the liquid crystal composition to immobilize thealignment of the liquid crystal, and the liquid crystal held the flowalignment.

Reference Example 14

A liquid crystal cell of Reference Example 14 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 360-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)in the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 15

A liquid crystal cell of Reference Example 15 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 370-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Reference Example 16

A liquid crystal cell of Reference Example 16 was produced by the samemethod as in Reference Example 9 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 380-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 370 nm and shielding of the display area of the liquid crystal cellfrom light make it possible to suppress the polymerization of themonomer represented by the chemical formula (6) at the same time ofcuring the sealing material.

Evaluation Test 5

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (5) used as the monomer, the following liquidcrystal cells of Reference Examples 17 to 20 were produced and examined.

Reference Example 17

A liquid crystal cell of Reference Example 17 was produced by the samemethod as in Reference Example 1 except that the compound represented bythe chemical formula (5) was used as the monomer, the amount of themonomer in the liquid crystal composition was 1.0% by weight in thewhole liquid crystal composition, and the whole liquid crystal cell wassubjected to the PS step such that it was irradiated with light at adose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 315-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)in the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 18

A liquid crystal cell of Reference Example 18 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 325-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)of the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 19

A liquid crystal cell of Reference Example 19 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 335-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Reference Example 20

A liquid crystal cell of Reference Example 20 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 345-nm band-passfilter with the display area of the liquid crystal cell shielded fromthe light. A realignment treatment of heating this liquid crystal cellat 130° C. for 40 minutes was performed. As a result, the flow alignmentof the liquid crystal was removed and the liquid crystal was uniaxiallyaligned without unevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 335 nm and shielding of the display area of the liquid crystal cellfrom light make it possible to suppress the polymerization of themonomer represented by the chemical formula (5) at the same time ofcuring the sealing material.

Evaluation Test 6

In order to examine the wavelength of light for curing the sealingmaterial which affects the polymerization of the compound represented bythe chemical formula (6) used as the monomer, the following liquidcrystal cells of Reference Examples 21 to 24 were produced and examined.

Reference Example 21

A liquid crystal cell of Reference Example 21 was produced by the samemethod as in Reference Example 17 except that the compound representedby the chemical formula (6) was used as the monomer and the whole liquidcrystal cell was subjected to the PS step such that it was irradiatedwith light at a dose of 1 J/cm² from an ultra-high-pressure UV lamp(USH-500D, manufactured by USHIO INC.) as a light source through a350-nm band-pass filter while shielding the display area from the light.A realignment treatment of heating this liquid crystal cell at 130° C.for 40 minutes was performed. As a result, the PS polymerizationproceeded in the region along the sealing material (the outer edge ofthe display area) in the liquid crystal composition to immobilize thealignment of the liquid crystal, and the liquid crystal held the flowalignment.

Reference Example 22

A liquid crystal cell of Reference Example 22 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 360-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the PS polymerization proceeded in theregion along the sealing material (the outer edge of the display area)in the liquid crystal composition to immobilize the alignment of theliquid crystal, and the liquid crystal held the flow alignment.

Reference Example 23

A liquid crystal cell of Reference Example 23 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 370-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Reference Example 24

A liquid crystal cell of Reference Example 24 was produced by the samemethod as in Reference Example 17 except that the whole liquid crystalcell was subjected to the PS step such that it was irradiated with lightat a dose of 1 J/cm² from an ultra-high-pressure UV lamp (USH-500D,manufactured by USHIO INC.) as a light source through a 380-nm band-passfilter while shielding the display area from the light. A realignmenttreatment of heating this liquid crystal cell at 130° C. for 40 minuteswas performed. As a result, the flow alignment of the liquid crystal wasremoved and the liquid crystal was uniaxially aligned withoutunevenness.

Consequently, shielding of light having a wavelength of at least shorterthan 370 nm and shielding of the display area of the liquid crystal cellfrom light make it possible to suppress the polymerization of themonomer represented by the chemical formula (6) at the same time ofcuring the sealing material.

Example 8

The present example utilized linearly polarized ultraviolet light at adose of 1.5 J/cm² from a UV-B ultraviolet lamp (FHF32-UVB, manufacturedby Sankyo Denki Co., Ltd.) in combination with a polarizing film for thePS treatment on the liquid crystal cell, although Example 1 utilizedunpolarized ultraviolet light. The degree of polarization was 10:1. Thepolarization direction was the same as the polarization direction oflight in the alignment treatment on the photo-alignment film. Except forthese conditions, a liquid crystal cell was produced in the same manneras in Example 1. The liquid crystal in this liquid crystal cell wasuniaxially aligned without unevenness, and the alignment characteristicof the liquid crystal was better than that in Example 1 and the contrastratio was about 10% higher than that of Example 1.

Example 9

A liquid crystal cell was produced in the same manner as in Example 2except that the same linearly polarized ultraviolet light as in Example8 was applied in the PS treatment. The liquid crystal in this liquidcrystal cell was uniaxially aligned without unevenness, and thealignment characteristic of the liquid crystal was better than that inExample 2 and the contrast ratio was about 10% higher than that inExample 2.

Example 10

A liquid crystal cell was produced in the same manner as in Example 5except that the same linearly polarized ultraviolet light as in Example8 was applied in the PS treatment. The liquid crystal in this liquidcrystal cell was uniaxially aligned without unevenness, and thealignment characteristic of the liquid crystal was better than that inExample 5 and the contrast ratio was about 5% higher than that inExample 5.

Example 11

A liquid crystal cell was produced in the same manner as in Example 6except that the same linearly polarized ultraviolet light as in Example8 was applied in the PS treatment. The liquid crystal in this liquidcrystal cell was uniaxially aligned without unevenness, and thealignment characteristic of the liquid crystal was better than that inExample 6 and the contrast ratio was about 10% higher than that inExample 6.

Example 12

A liquid crystal cell was produced in the same manner as in Example 7except that the same linearly polarized ultraviolet light as in Example8 was applied in the PS treatment. The liquid crystal in this liquidcrystal cell was uniaxially aligned without unevenness, and thealignment characteristic of the liquid crystal was better than that inExample 7 and the contrast ratio was about 10% higher than that inExample 7.

The present application claims priority to Patent Application No.2011-183797 filed in Japan on Aug. 25, 2011 under the Paris Conventionand provisions of national law in a designated State, the entirecontents of which are hereby incorporated by reference.

REFERENCE SIGNS LIST

-   3, 33, 43, 53, 63: polymerizable monomer-   10: array substrate-   11, 21: transparent substrate-   12, 22: horizontal alignment film-   13, 23: PS layer (polymer layer)-   20: color filter substrate-   30: liquid crystal layer-   32, 42: alignment film-   33 a, 43 a: polymerizable monomer (not excited)-   33 b, 43 b: polymerizable monomer (excited)-   52: photoactive group (vertical alignment film molecule)-   54, 64, 74: liquid crystal molecules-   55: hydrophobic group-   62: photoactive group (horizontal alignment film molecule)-   71: slitted electrode-   71 a: slit-   72: plate electrode-   81: sealing material

1. A method for manufacturing a liquid crystal display device,comprising the steps of: forming a horizontal alignment film containinga photoactive material on at least one substrate of a pair ofsubstrates; dropping a liquid crystal composition containing a liquidcrystal material and a monomer on one substrate of the pair ofsubstrates, the monomer being contained in an amount of 1.0% by weightor less in the whole liquid crystal composition; curing a sealingmaterial applied to one substrate of the pair of substrates along anouter edge thereof by irradiating the sealing material with light whosewavelength is 40 nm or more longer than an absorption wavelength edge ofthe monomer; and forming a polymer layer that controls the alignment ofliquid crystal molecules adjacent thereto on the horizontal alignmentfilm by irradiating the liquid crystal composition sealed between thepair of substrates with light to polymerize the monomer.
 2. A method formanufacturing a liquid crystal display device, comprising the steps of:forming a horizontal alignment film containing a photoactive material onat least one substrate of a pair of substrates; dropping a liquidcrystal composition containing a liquid crystal material and a monomeron one substrate of the pair of substrates; curing a sealing materialapplied to one substrate of the pair of substrates along an outer edgethereof by heating without light irradiation; and forming a polymerlayer that controls the alignment of liquid crystal molecules adjacentthereto on the horizontal alignment film by irradiating the liquidcrystal composition sealed between the pair of substrates with light topolymerize the monomer.
 3. A method for manufacturing a liquid crystaldisplay device, comprising the steps of: forming a horizontal alignmentfilm containing a photoactive material on at least one substrate of apair of substrates; applying a sealing material onto one substrate ofthe pair of substrates along an outer edge thereof; bonding the pair ofsubstrates; curing the sealing material; vacuum-injecting a liquidcrystal composition containing a liquid crystal material and a monomerinto between the pair of substrates; and forming a polymer layer thatcontrols the alignment of liquid crystal molecules adjacent thereto onthe horizontal alignment film by irradiating the liquid crystalcomposition sealed between the pair of substrates with light topolymerize the monomer.
 4. (canceled)
 5. The method for manufacturing aliquid crystal display device according to claim 1, wherein thephotoactive material is a photo-alignment film material.
 6. The methodfor manufacturing a liquid crystal display device according to claim 5,wherein the photo-alignment film material includes a compound containinga cyclobutane skeleton.
 7. The method for manufacturing a liquid crystaldisplay device according to claim 5, wherein the photo-alignment filmmaterial includes a compound containing either one of or both of aphotoisomerizable functional group and a photodimerizable functionalgroup.
 8. The method for manufacturing a liquid crystal display deviceaccording to claim 7, wherein the photoisomerizable or photodimerizablefunctional group is a cinnamate group or a derivative thereof.
 9. Themethod for manufacturing a liquid crystal display device according toclaim 5, wherein the light used in the step of forming a polymer layerthat controls the alignment of liquid crystal molecules adjacent theretoon the horizontal alignment film by polymerizing the monomer is linearlypolarized light.
 10. The method for manufacturing a liquid crystaldisplay device according to claim 1, wherein a polymerizable functionalgroup of the monomer is an acrylate group, a methacrylate group, a vinylgroup, or a vinyloxy group.
 11. The method for manufacturing a liquidcrystal display device according to claim 1, wherein the liquid crystalcomposition contains liquid crystal molecules including a multiple bondother than conjugated double bonds of a benzene ring in a molecularstructure thereof.
 12. The method for manufacturing a liquid crystaldisplay device according to claim 11, wherein the multiple bond is adouble bond.
 13. The method for manufacturing a liquid crystal displaydevice according to claim 12, wherein the double bond is present in analkenyl group.
 14. The method for manufacturing a liquid crystal displaydevice according to claim 1, wherein the alignment mode of the liquidcrystal layer is an IPS mode, an FFS mode, an OCB mode, a TN mode, anSTN mode, an FLC mode, or a PDLC mode.
 15. The method for manufacturinga liquid crystal display device according to claim 14, wherein at leastone of the pair of substrates includes a multi-domain structure.